1. Field of the Invention
This invention relates to a developing roller and a method of producing the same as well as a process for inspecting a developing roller, and more particularly to a developing roller controlling a scattering of toner feed quantity and capable of forming a good image and a method of producing the same.
2. Description of the Related Art
In the image forming apparatus of an electrophotographic system such as copier, printer or the like, there is known a pressurized developing method as a developing method wherein toners are fed to a photosensitive drum keeping a latent image and then the toners are adhered to the latent image on the photosensitive drum to visualize the latent image. In this pressurized developing method, the image development is carried out, for example, by charging a photosensitive drum to a constant potential, forming an electrostatic latent image on the photosensitive drum through an exposure equipment and contacting a developing roller carried with toners onto the photosensitive drum kept with the electrostatic latent image to adhere the toners to the latent image on the photosensitive drum.
In the pressurized developing method, since the developing roller should be rotated while surely holding a state of being attached firmly to the photosensitive drum, it has a structure of forming a semi-conductive elastic layer made from a semi-conductive elastomer, which is formed by dispersing carbon black or metal powder into an elastomer such as polyurethane, silicone rubber, acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), epichlorohydrin rubber (ECO) or the like, or a foamed body thereof on an outer periphery of a shaft made from a good conductive material such as a metal or the like. Also, a surface covering layer may be further formed on the surface of the above elastic layer for the purpose of controlling the charging characteristics and adhesion property to toners and preventing the contamination of the photosensitive drum with the elastic layer, and the like.
In the developing roller having the above construction, it is generally required to optimize the toner feed quantity for forming a good image without causing image fault such as fog or the like. As to such a requirement, there has hitherto been known a method wherein the toner feed performance of the developing roller is improved by changing the surface roughness of the developing roller or changing the polishing method of the surface to adjust the surface form of the developing roller (see, for example, JP-A-2000-206779, JP-A-H08-123191 and JP-A-H08-286501).
However, there is a problem that even when the surface form of the developing roller is adjusted by the above method, the scattering of the toner feed quantity is caused by the resulting developing roller.